Stable crystalline lattices in two-dimensional binary mixtures of dipolar particles

Abstract

The phase diagram of binary mixtures of particles interacting via a pair potential of parallel dipoles is computed at zero temperature as a function of composition and the ratio of their magnetic susceptibilities. Using lattice sums, a rich variety of different stable crystalline structures is identified including AmBn structures. [A (B) particles correspond to large (small) dipolar moments.] Their elementary cells consist of triangular, square, rectangular or rhombic lattices of the A particles with a basis comprising various structures of A and B particles. For small (dipolar) asymmetry there are intermediate AB2 and A2B crystals besides the pure A and B triangular crystals. These structures are detectable in experiments on granular and colloidal matter.

Nonadditivity in the effective interactions of binary charged colloidal suspensions

“…Even if this interaction is pairwise additive, the full calculation of structure and phase behaviour has only been done for selected cases. Among those are hard spheres [4][5][6][7], oppositely charged colloids [8,9], twodimensional dipolar mixtures [10,11] and two-dimensional Yukawa mixtures [12].…”

Binary crystals in two-dimensional two-component Yukawa mixtures

“…Given the fact that the phase behavior is getting increasingly complicated upon lowering Z, involving a huge basket of candidates, we only present results starting from Z = 0.2. Furthermore, in contrast to situations where the pair potential can be described as a power low of the separation distance (as it was the case in our previous work on dipolar mixtures [9]), the phase diagram becomes pressure dependent for Yukawa systems. To capture this feature, we present results at three well distinct pressures, namely p * ≡ p/(V 0 κ 3 ) = 0.01, 1 and 100.…”

“…These are highly decorated by a basis involving either A particles alone or both B and A particles. The topology of the resulting phase diagram differs qualitatively from that of hard disk mixtures [8] and dipoles [9].…”

“…Binary mixtures in two dimensions have been studied for hard disks [8] and a complex diagram of close packing was obtained as a function of their diameter ratio. More recently, a two-dimensional binary mixture with soft interactions was considered [9], namely that for parallel dipoles where the pair potential scales with the inverse cube of the interparticle separation. A variant of this model has been considered in Ref.…”

“…In particular for low asymmetries, the hard disk system shows a complete separation into pure A and B triangular crystals [8] while the soft dipolar systems possesses two stable mixed crystals as well with stoechiometric ratio A 2 B and AB 2 [9]. These differences show that the topology of the phase diagrams depend on details of the interactions and there is certainly a need to understand this dependence in more detail.…”